#include<stdio.h>
int  main()
{
    const double PI=3.1415926;
    double r,circumference,area;
    printf("请输入圆的半径:");
    scanf("%if",&r);
    circumference = 2*PI*r;
    area = PI * r * r;
    printf("周长 = %.3f\n",circumference);
    printf("面积 = %.3f\n",area);
    return 0;
}